I. Field of the Invention
The present invention is generally directed to tissue contour modifying implantable prostheses for use in plastic and reconstructive surgery and, more particularly, to a bio-compatible, excretable gel containing an organic polymer material for use within a flexible prosthesis membrane.
II. Discussion of the Related Art
Implantable silicone and other plastic prosthesis materials for correcting contour defects and form limitations in the human body have been in use since at least the early 1950's. This procedure has been most frequently used for breast reconstruction, either following traumatic or surgical loss of the breast tissue, as through radical mastectomy, or to correct developmental hypoplasia.
Typically such an implant has consisted of a flexible outer shell member made from silicone rubber, polyurethane or other known durable bio-compatible polymer which has an elastic memory and is configured to a shape dedicated to provided the desired bodily contour. The generally hollow shell member may consist of a single layer or double layer in which one shell is placed inside the other.
Many substances have been used to fill the lumen of the implant. Examples of these include normal saline, foam pads and silicone oil or silicone gel. Each of the prior materials, however, exhibit at least one major drawback. Saline, for example, is a poor lubricating agent and such prostheses filled only with saline have been known to undergo accelerated shell breakdown and rupture due to friction of the inner shall rubbing against itself. Molded foam inserts enjoyed a relatively short period of popularity because such materials were found to rapidly calcify after implantation in the body.
After a considerable period of time, silicone oil remains the most commonly used filling material. With respect to most implant prostheses including breast implants, the filler is normally utilized in the form of a partially vulcanized silicone which is sealed inside the lumen prior to implant. This material has enjoyed a long period of use principally because of two desirable properties. Silicone oil is a natural lubricant and this tends to prevent shell breakdowns occasioned by internal friction. In addition, the viscosity of silicone oil placed inside a partially inflated lumen imparts a consistency to the structure which closely predicates natural breast tissue.
Despite its widespread acceptance, the use of silicone oil does present several major disadvantages. One such disadvantage involves the inability of the body to eliminate silicone oil. The silicone oil continually migrates through the wall of the implant into surrounding tissue where, because is not eliminated by the body, it can accumulate and produce a painful inflammatory reaction. In the case of traumatic rupture of the shell, silicone is forced into the surrounding tissues, travelling down the facial planes where it causes a severe foreign body reaction and requires extensive surgery to remove. An additional drawback with respect to silicone oil is that it is radiographically dense. This makes it more difficult to examine the area of implant by x-ray, or the like. This may obscure mammogram detail and delay detection of breast cancer.